1. Field of the Invention
This invention relates to nickel (II) thiobis-(alkylphenolates) complexed with hydroxyl-substituted ligands such as alcohols and phenols as novel compounds and to organic compositions, normally subject to oxidative degradation such as lubricants and plastics, containing a minor amount of said nickel thiobis(alkylphenolate) complex sufficient to impart antioxidant and ultra-violet stabilization thereto.
Another aspect of this invention is directed to compositions containing the above-referred to novel complexes in which the compositions comprise said complexes and an organic medium selected from oils of lubricating viscosity or greases prepared therefrom, said oils may be hydrocracked lubricating oils, hydraulic oils, automotive oils, gear oils, or transmission fluids, waxes, liquid hydrocarbon fuels, and distillate fuel oils wherein said oils may be mineral oils or fractions thereof or synthetic hydrocarbon base oils. The additive compounds cited hereinabove are also useful for stabilizing plastics e.g. polyolefins against thermally or light catalyzed oxidative degradation. These fluids normally require the presence of stabilizing agents to inhibit oxidative degradation catalyzed inter alia by ultraviolet light, the presence of metals or resulting from high temperature and other high energy conditions.
2. Description of the Prior Art
The production of lubricant compositions, for example, lubricating oils produced by hydrocracking provides a relatively high viscosity index oil and permits the use of base stocks that would be unsuitable for other purposes. On the other hand, however, hydrocracked lubricating oils tend toward poor stability against ultraviolet light degradation, rapidly forming suspended and/or precipitated insoluble material on exposure to ultraviolet light, such as sunlight, or other sources of actinic radiation. Additionally lubricants may be subjected to high temperatures which tend as mentioned heretofore to catalyze oxidative degradation.
Commercially available ultraviolet stabilizers are listed by class and function and identified as to structure in the Kirk-Othmer Encyclopedia in "Encyclopedia of Chemical Technology"; Second Edition, Vol. 21, pp. 115-122. U.S. Pat. No. 3,832,304 discloses the use of aromatic azo compounds for stabilizing hydrocracked oils. U.S. Pat. Nos. 2,703,786; 2,716,090 and 3,210,277 disclose the use of polyvalent metal, e.g., Ni salts of thiobis(alkylphenols) as oxidation inhibitors and plasticizing agents. Nickel thiobis-(4-t-octylphenolate) is disclosed in U.S. Pat. No. 2,971,940 as a stabilizer for plastics and complexes thereof with amines, e.g., n-butylamine are disclosed in U.S. Pat. No. 3,215,717 as plastic stabilizers. However, there are believed to be no disclosures of these compounds in oils and lubricants. Further none of the foregoing disclosures are directed to organic compositions containing the organo-sulfur-nickel complexes described in accordance with this invention. The subject complexes with hydroxy-substituted ligands are not disclosed by any prior art known to applicant. Accordingly, their use in various compositions comprising organic media such as oils of lubricant viscosity and plastics to impart resistance to oxidation and other induced degradation is also believed to be novel. Therefore, their combination with co-antioxidants such as diarylamines, phenothiazines, etc. is synergistic in controlling oxidation, shows a remarkable degree of improvement at low total additive concentrations, and/or has unusual effectiveness in controlling the formation of sludges commonly observed in the use of such co-antioxidants is also believed to be novel. They are especially useful in imparting protection to lubricant base stocks, e.g. paraffinic hydrocarbons, refined petroleum products and synthetic base stock, e.g., ester base stocks.